The present invention relates to an information processing system wherein at least one microprogram-controlled type arithmetic processing unit freezes the internal state of the unit by a microprogram and notifies another unit of a demand for communication by the microprogram.
In an information processing system including a plurality of arithmetic processing units, if a fault occurs in one of the arithmetic processing units, a fault report signal is given to the system control unit, which then remedies the fault by the use of a processor relieving technique. For details of this technique, reference may be made to the U.S. Pat. No. 4,443,849.
Meanwhile, if the firmware of one of the arithmetic processing units requires clock synchronization with the timers of all the other processing units, the communication demand from the firmware will also be given to the system control unit as the aforementioned fault report signal. Therefore, in response to the fault report signal, the system control unit has to process distinction as to whether or not to remedy the fault. As a result, there is the disadvantage that the system control unit has to execute very complex processing and spend much time for this fault remedying.